EVALUATION & ASSESSMENT OF VARIATION IN … resolution in images of high ... CBCT generated lateral...
Transcript of EVALUATION & ASSESSMENT OF VARIATION IN … resolution in images of high ... CBCT generated lateral...
University J Dent Scie 2015; 1(2) : 15-18
ABSTRACT : Aim: To assess the variations in linear parameters of left, right & combined cephalograms (CBCT) & to establish a method of quantifying skeletal asymmetries which will aid in treatment planning during orthognathic surgeries. MATERIAL AND METHODS: Pre Orthodontic anonymised CBCT scans of 32 healthy adults of age 18-28 years. The DICOM images were loaded into Dolphin 11.5,orientation of hard & soft tissue was done in a horizontal & vertical plane. The scans were then cut from the middle half in a vertical plane to make it as a right & a left half & a combination view is also taken. Two dimensional lateral cephalograms which were then loaded to Dolphin was used to Digitize for cephalometric tracings of the two dimensional images. 8 parameters were traced. RESULTS: No Statistical significant difference between the right side and the combined view (p > 0.05), also no statistical significant difference between the left side measurement and the combined measurement (p > 0.05)was present. CONCLUSION: CBCT generated lateral cephalograms computed by the dolphin software are extremely accurate & can be used for craniofacial analysis.
1 2 3 4 5Surabhi Singh, Rajesh B Dhirawani, Jayant Marya, Siddharth Singh, Anup Belludi and Priyanka Dausage1 2 3 Senior Lecturer , Department of Orthodontics and Dentofacial Orthopedics Professor and Head,
4 P.G student 2nd year, Senior Lecturer, Department of Oral and Maxillofacial Surgery,6 Senior Lecturer , Department Of Pedodontics and Preventive Dentistry Hitkarini Dental College,
5and Hospital, Jabalpur, India Professor ,Department of Orthodontics and Dentofacial Orthopedics KLE, No. 20, Yeshwanthpur, Suburb, IInd Stage, Tumkur Road, Bengaluru, Karnataka
INTRODUCTION : Digital imaging is the display of
filmless radiographs. More importantly the images are
captured in a computer & displayed almost instantly,
facilitating operative procedures that now can be image 1 guided. Before the invention of the cephalometer, knowledge
regarding the process of facial growth was based heavily on
skeletal material that was by its nature cross-sectional.
The strength of the cephalometric technique was that it
allowed the longitudinal study of changes in the growing face.
CBCT images offer new information about patients. Since its
introduction in 2001, 3D cone beam imaging has shown
logarithmic growth. The image contains information that is
simply not seen on a traditional cephalometric image. As
health care professionals, orthodontists naturally want to
improve patient care. One way to improve patient care is to 2 have better information about the patient's problem.
There is already evidence that the treatment of some
orthodontic conditions, such as supernumerary and impacted
teeth, benefit from 3D imaging. Surgical planning for patients
with jaw asymmetry e.g – Hemifacial Microsomia can benefit
from 3D imaging. This allows measurements of true
dimensions without the customary problems of
magnification, superimposition & distortion.Therefore, one
of the reasons CBCT scanning is gaining momentum in
clinical practice is the desire for excellence in patient care.3
With the CBCT, a full scan of the head can be performed, in a
few seconds during which the patient receives an effective
dose of only about 50 µSv, which equals the total dose of
conventional radiographs that are now considered essential
for almost every orthodontic patient, such as the lateral 4cephalogram & the panoramic radiographs.
MATERIAL & METHOD : 32 Pre orthodontic anonymised
CBCT scans belonging to patients available with the Imaging
Centers at Delhi (Mahajan Imaging Diagnostic Centre) &
Bombay (Insight CBCT Centre).
The raw images were exported using i-CAT Vision software
into DICOM files. The DICOM images were loaded into
Dolphin 11.5 software, then the orientation of hard tissue was
done in a horizontal plane & vertical plane( Figure 1), then the
soft tissue orientation was done over the hard tissue( Figure
2). The CBCT scan were then cut from the middle half in a
vertical plane to make it as a right half & a left half. A
combination view was also taken in which left side was
EVALUATION & ASSESSMENT OF VARIATION IN LINEAR PARAMETERS OF LEFT, RIGHT AND COMBINED CEPHALOGRAMS GENERATED BY CONE BEAM COMPUTED TOMOGRAPHY
Journal of Dental Sciences
University
Key Words : Cone Beam Tomography, Cephalogram, Dolphin software
Source of support : NilConflict of interest : None
OriginalResearch
Paper
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superimposed on the right side.
Figure 1 : Showing Orientation Of Mid-sagittal & Axial
Planes In Hard Tissue Front
Figure 2: Showing Orienting The Soft Tissue Over The Hard
Tissue Front
Using this procedure the CBCT scan of 1 patient was made
into 3 two- dimensional lateral cephalograms which were
then loaded to Dolphin (10.5 version) was used to 'Digitize'
for cephalometric tracings of the 2D images ( Figure 3).
Following landmarks were traced on Dolphin10.5 (Figure 4):
N – Ans, Ans – Me, S – Go, Ptm – Ans, Co – Gn, Co – A, Co –
Go, Go – Me
Figure 3: Showing Derived 2d Lateral Cephalogram Using
3d Models
Figure 4: Cephalometric Tracing Done On Dolphin
RESULTS : No Statistical significant difference between the
right side and the combined view (p > 0.05), also no statistical
significant difference between the left side measurement and the
combined measurement (p > 0.05)was present.
DISCUSSION: Cone Beam Computed Tomography offers
elaborate information about the details of the patient's images
that cannot be observed on the conventional cephalogram
images. With the increasing use of Cone beam Computed
Tomography application in Orthodontic treatment planning in
certain conditions such as supernumerary teeth, impacted teeth
& more importantly in patients requiring orthognathic surgeries
specially with skeletal asymmetries, as 3D images give more
University J Dent Scie 2015; 1(2) : 15-18
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University J Dent Scie 2015; 1(2) : 15-18
information pertaining to the left & the right sides than
compared to conventional cephalograms which give only 2D
information.
Cone beam computed tomography (CBCT) technique
presents an innovation of tomographic imaging systems and
subsequent volumetric image reconstruction for dentistry.
When compared with other methods of tomographic imaging
CBCT is characterized by rapid volumetric image acquisition 5from a single low radiation dose scan of the patient.
CBCT systems have been designed for imaging hard tissues
of the maxillofacial region. CBCT is capable of providing
sub-millimetre resolution in images of high diagnostic
quality, with short scanning times (10–70 seconds) and
radiation dosages reportedly up to 15 times lower than those 6of conventional CT scans.
In orthognathic surgeries like Bilateral Saggital Split
Osteotomy Pre surgical & post surgical CBCT scans can be
done with 3D models registered on the surface of cranial base.
They can be later on superimposed to know the location,
magnitude & direction of the mandibular displacement. This
would be helpfull in quantification of vertical, transverse &
antero-posterior ramus displacement, & it has been concluded
that CBCT allows clinically accurate & reliable 3D linear 7measurements of craniofacial complex.
Studies to determine the accuracy & reliability of 3D cranio-
facial measurements obtained from CBCT scans of a dry
human skull have been done. Inter-landmarks linear
measurements are made directly on the skull & compared
with the same measurements made on CBCT scans. When
evaluated CBCT allows clinically accurate & reliable 3D 8linear measurement of craniofacial complex.
Comparison of accuracy of craniometric measurements have
been done on lateral cephalograms & on CBCT images with
fiducial markers placed on known craniometric landmarks of
dry skull & have been evaluated using CBCT & conventional
lateral head films were taken subsequently. All measurements
were repeated within a one-month interval, and intra-class
correlations were calculated & it was observed that no
statistically significant difference was noted between CBCT
measurements & direct craniometric measurements. 2D
cephalometric norms cannot be readily used for 3D
measurements because of differences in measurement 9accuracy between the two exams.
The aim of this study was to evaluate the lateral cephalograms
data's from computer generated Cone Beam Computed
Tomography scans. Assessment of the variations in linear
parameters of left, right & combined cephalograms were done to
establish a accurate and reliable method of evaluating
cephalograms which can help orthodontists & maxillofacial
surgeons understand & quantify the extent of skeletal
discrepancy precisely & to establish a method of quantifying
skeletal asymmetries which will aid in treatment planning during
orthognathic surgeries.
Few studies have beent attempted to assess the accuracy of
cephalometric measurments as applied three dimensionally
because of known intrinsic limitations of these images, such as 10 distortion & magnification. No statistically significant
difference was found between the CBCT measurments of left,
right & the combination side, & the p value is showing that p >
0.05.
Although the statistical results are insignificant there is a high
level of reliability, accuracy & reproducibility which make it
clinically significant. The maxilllary length was measured from
Co – A & Ptm – Ans this would help us observe if there is a
unilateral discrepency. N - Ans will help us to evaluate the upper
anterior facial height in cases of vertical maxillary excess
patients. Ans – Me indicates the lower anterior facial height &
any discrepency can be accurately quantified. Previous studies
have shown that there is more skeletal discrepency & facial
asymmetries in the mandible than in the maxillla especially in
skeletal class III patients & some of these patients fall into the
category of surgical envelope of discrepency. In such cases high
reliability of unilateral landmarks are necessary. The parameters
which we have considered like Co – Gn, Co – Go & Go – Me will
show if there is any skeletal asymmetry in the mandible. The
parameter S – Go shows the posterior facial height & the
measurments on the left & right side indicate if there is any
discrepency present.
Several Studies have been done to evaluate the precision of
cephalometric landmark identification using the CBCT &
Conventional cephalometric views & have concluded that
CBCT volume images provide generally more precise
identification of traditional cephalometric landmarks. More 11precise location of the Condyle & Gonion has been observed.
In this study DICOM files were used to create 2 dimensional
radiographs on Dolphin Cephalomertic software & a method of
evaluating unilateral & bilateral landmarks was established. The
number of clinicians using 3 dimensional records during
diagnosis & treatment planning stages are increasing steadily.
The purpose of this study was to give the clinician a reliable
method of quantifying the measurements on a lateral
cephalogram using images generated from CBCT to overcome
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University J Dent Scie 2015; 1(2) : 15-18
the drawbacks of Conventional cephalograms like projection
errors, magnification errors & limitations of 2D over 3D.
SUMMARY & CONCLUSION : In this study pre
anonymised CBCT scans of 32 patients belonging to age
group of 18 – 25 years were analysed. All the CBCT scans
were taken by i-CAT (Imaging Science International,
Germany) & the images were exported using i-CAT vision
software.
Although the statistical results are insignificant there is a high
level of reliability, accuracy & reproducibility which make it
clinically significant. The maxilllary length was measured
from Co – A & Ptm – Ans this would help us observe if there
is a unilateral discrepency. N - Ans will help us to evaluate the
upper anterior facial height in cases of vertical maxillary
excess patients. Ans – Me indicates the lower anterior facial
height & any discrepency can be accurately quantified. The
parameters which we have considered like Co – Gn, Co – Go
& Go – Me will show if there is any skeletal asymmetry in the
mandible. The parameter S – Go shows the posterior facial
height & the measurments on the left & right side indicate if
there is any discrepency present.
Lateral cephalograms are 2 dimensional & have intrinsic
limitations that result in distorted images & magnification
errors. CBCT generated lateral cephalograms computed by
the dolphin software are extremely accurate & can be used for
craniofacial analysis.
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CORRESPONDANCE:
Dr. Priyanka Dausage
34, Nayagaon, P.O. Vidyut Nagar
Jabalpur 482008, India
E-mail : [email protected]
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